Induction furnace



March 16, 1965 A. A. cOLEY 3,173,982

INDUCTION FURNACE Filed Aug. 10, 1961 INVENTOR. ALFRED A. COLEY Maw ATTORNEY 3,173,982 Patented Mar. 16, 1965 New Jersey Filed Aug. 10, 1961, Ser. No. 130,659 8 Claims. (Cl. 13-29) This invention relates to an induction furnace, and more particularly to a rotary drum type induction furnace provided with a novel inductor mounting throat opening.

In a conventional induction furnace having a single coil low frequency inductor, the throat opening is generally rectangular in shape having dimensions of approximately eight inches by twenty-eight inches. The twentyeight inch dimension of the throat opening has been conventionally disposed so as to extend in a direction parallel to the longitudinal axis of the drum. In a so-called twin coil inductor, the throat opening is usually about fifty-six inches long and eight inches wide. Thus, the so-called twin coil inductor is associated with a throat opening which is approximately twice as long as the throat open-" ing for a single coil inductor.

It has been conventional heretofore to provide the 28-inch or 56-inch dimension of the throat opening parallel to the longitudinal axis of the drum. For example, see FIGURES 1 and 2 of Patent 2,474,443. In order to make a drum with the conventional throat opening, it is necessary to form the throat opening either with bricks or with some type of monolithic lining, so that the arch which forms the drum lining can be made continuous. Also, there must be a certain amount of archwork in the brick lining over the throat opening in the drum parallel to the longitudinal axis of the drum.

When it is desired to make a monolithic lining around the throat opening, it is customary to put in the lining first and then lay the drum arch against it. This is undesirable since the bricklayers will be working over the green monolithic lining. The possibility of severely damaging a green lining by laying bricks over it and walking on it is probable. Accordingly, it is preferable to form the monolithic lining after the brickwork is installed.

if the monolithic lining is to be formed after the brickwork is installed, it is necessary to provide a brick arch or corbell over the throat opening. it is preferable to avoid the expense of making such a special brick arch. Also, the necessary rise of such an arch will require the use of more monolithic material than would ordinarily be needed. if the area around the throat opening is corbelled, the resulting structure has very little strength until the monolithic lining is installed and cured.

in addition to the above-mentioned problems associated with the manufacture of induction furnaces, the position of the throat opening seriously weakens the bottom portion of the drum. if an elongated slot is provided on the top of the drum along the longitudinal axis of the drum for charging large items into the drum, the drum is seriously weakened to the point of being dangerous. Accordingly, it is necessary for the drum to have a sub stantial portion which is a complete solid ring if the monolithic lining is to be formed at the end of the manufacturing stage of the drum. Also, such portion of the brick lining which is a complete ring must be of sufficient strength so as to withstand the compressive stresses which develop in it due to the weight of the brickwork.

In accordance with the present invention, the longest dimension of the throat opening is arcuate and lies in a plane which is perpendicular to the longitudinal axis of the drum. In this manner, the cut in the archwork will be approximately 25-inches which is shorter than the actual throat length in a single coil inductor. Also, the amount of corbelling is greatly reduced since a substantial portion of the drum arch is completely closed on itself. Also, the bottom portion of the drum may be of suiiicient strength so as to absorb the shock when large metallic objects are thrown into the drum. In a conven tional furnace, wherein the throat opening extends along the bottom portion of the drum for a distance of approximately 56-inches, the presence of the throat opening weakens the bottom portion of the drum so that care must be exercised when charging such a drum with large metallic objects.

It is an object of the present invention to provide a novel induction furnace wherein the throat opening for the inductors lies in a plane substantially perpendicular to the longitudinal axis of the drum.

It is another object of the present invention to provide a novel rotary drum type induction furnace wherein the lengthwise dimension of the inductor throat opening extends in a transverse direction toward the pouring spout as compared with a conventional throat opening which has its lengthwise dimension extending in a longitudinal direction on the drum.

It is still another object of the present invention to provide a novel rotary drum type induction furnace having a throat opening disposed so as to provide for increase strength of the bottom portion of the drum and substan tially reduce the complexity of the brickwork lining within the drum.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a transverse sectional view of a rotary drum type furnace in accordance with the present invention.

FIGURE 2 is a partial longitudinal sectional view of the rotary drum type furnace illustrated in FZGURE 1 taken along lines 22 in FIGURE 1.

Referring to the drawing in detail, wherein like numerals indicate like elements, there is shown in FIGURE 1 a rotary drum type furnace designated generally as 16'.

The furnace lib comprises a drum 12 having an outer lining 14- secured to an outer layer 16 of refractory brick. The lining 14 may be a layer of asbestos material as is conventional in the art. The drum 12 also includes an inner layer it; of refractory brick.

The drum 12 is provided with end walls 20 and 22. The end wall it? is provided by a single row of refractory bricks 24 which may be covered by the lining 14. The end wall 22 is provided by a single row of refractory bricks 26 and may be covered by an extension of the lining 14.

The end wall 22 is provided with an opening 28 as shown more clearly in FIGURE 1. The opening 28 is coextensive with the passage in the door sill 30. The passage in the door sill St is selectively closed by means of a door 32.

The drum 12 is provided with a pouring spout 34. The spout 34 is provided with an opening 36 in communication with the interior of the drum 12. The bottom portion of the drum 12 includes a monolithic lining 38 having a throat opening 40 therein.

As shown more clearly by a comparison of FIGURES 1 and 2, the longest dimension of the opening 49 is sufiicient to accommodate a twin coil inductor. Thus, the length of the opening 40 as illustrated in FIGURE 1 is approximately 56-inches long. Tle width of the opening 46 as illustrated in FIGURE 2 varies from 5- inches at the bottom portion to 8-inches at the top portion adjacent the inner peripheral surface of the layer 18 of refractory bricks. It will be noted that the longest dimension of the throat opening 46 extends in a direction which is perpendicular to the longitudinal axis of the drum 12.. Thus, the throat opening 40 extends around the drum 12 rather than along the length of the drum 12 as was conventional heretofore.

The throat opening 4i? provides communication between the interior of the drum l2 and the melting loops of the inductor units. The melting loops comprise a melting channel 42 extending parallel and below the throat opening 40'. Connecting channels 44, 46 and 43 provide communication between the melting channel 42 and the throat opening 46. Thus, a melting loop is provided around the coil windings 5d and 52.

The melting loops and the structure of the inductor units are conventional and per se form no part of the present invention. These elements are preferably disposed within a casing as is conventional in the art and illustrated in Patent 2,474,443. In view of the generally known arrangement and structure of these elements, a more detailed description is not deemed to be necessary.

The operation of a rotary drum furnace is well known to those skilled in the art and it is not deemed necessary to explain the same in order to have an understanding of the present invention. Thus, the operation of the furnace It the manner of charging the same, and the manner of pouring the molten metal therefrom by means of the spout are well known to those skilled in the art.

It will be noted that the disposition of the throat opening it) substantially increases the length of the uninterrupted portion of the bottom section of the drum 12. Thus, articles charged into the drum 12 through the door sill will be redeposited on such bottom section spaced from the throat opening 46. If desired, the drum 12 of the present invention may be provided with a top opening such as illustrated in the above-mentioned patent. In such a case, the top opening will be spaced longitudinally along the length of the drum 12 so as not to be directly over the throat opening 40.

It will be noted that the center line 66 of the inductor units intersect the diameter 62 of the drum 12 at an acute angle alpha. The diameter 62 bisects the opening 28. As shown, the angle alpha is approximately 20. Angle alpha may be any angle between zero and 45 in the lower left quadrant with respect to the diameter 62 as dictated by the requirements of the objects of the furnace 10.

The amount of metal left in an induction furnace when all but sufiicient metal to cover the throat opening 4% has been removed is called the heel or the button. By adjusting the angle alpha, a large or small heel may be obtained. For example, a small angle alpha provides a large heel which is often desirable. A large angle alpha provides a small heel since the metal will drain into the area between the throat opening 4% and the spout 34. Such an arrangement is often advantageous and provides for rapid drainage of the heel.

It will be noted that the throat opening 46: is in line with the spout opening 3d as shown more clearly in FIGURE 2. Thus, it is possible to use the access provided by the spout 34 to clean the throat opening when necessary. Also, the alignment of the spout 34 and throat opening 46 provides the access required when applying a gas torch to fire the lining or for preheating prior to filling with molten metal.

It will be obvious to those skilled in the art that conventional elements such as the means for rotating the drum 12 are not illustrated in the drawing. It is believed that conventional elements of this nature need not be illustrated or discussed in order to have an understanding of the present invention.

Thus, it will be seen that the present invention provides a drum for induction furnaces which has increased strength and greatly simplifies the brickwork necessary to make a refractory lining. Also, the disposition of the throat opening enables a smaller amount of monolithic material to be utilized while providing for varied drainage of the heel.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the fore going specification as indicating the scope of the invention.

I claim:

1. A rotary drum type induction furnace wherein a cylindrical drum is rotatably mounted about an axis, said drum having a refractory lining, the lining having a throat opening therein which is at least partially rectangular shaped in cross-section, the opening being in communication with the interior of said drum, a pouring spout on said drum in communication with the interior of said drum, an inductor unit mounted below said throat opening, means providing channels around said inductor unit, said channels being in communication with said opening, the improvement wherein the lengthwise dimension of the rectangular shaped portion of said opening extends in a direction substantially perpendicular to said axis.

2. In a rotary drum type induction furnace comprising a cylindrical drum having a refractory lining, said lining having a substantially rectangular shaped throat opening therein, a pouring spout on said drum, means on said drum for introducing material to be melted into the interior of said drum at a point longitudinally spaced from said opening, and the lengthwise dimension of said opening extending in a direction substantially perpendicular to the axis about which said drum is adapted to rotate.

3. In a rotary drum type induction furnace comprising a cylindrical drum having a refractory lining, said lining having a rectangular shaped throat opening therein, said throat opening being in communication with the interior of said drum, and the lengthwise dimension of said opening extending in a circumferential direction substantially perpendicular to the longitudinal axis of said drum and toward an opening in said drum providing communication between a pouring spout and the interior of said drum.

4. In a furnace in accordance with claim 3 including a charging opening in said drum, said charging opening being bisected by a diameter of said drum, said diameter forming an acute angle with a center line of an inductor unit in said throat opening, said acute angle being in the third quadrant with respect to said diameter.

5. In a furnace in accordance with claim 4 wherein said acute angle is less than 45.

6. In a rotary drum type induction furnace comprising a cylindrical drum having a refractory lining, said lining having an elongated rectangular shaped throat opening in communication with the interior of said drum, said drum being adapted to rotate with its longitudinal axis being horizontally disposed, the lengthwise dimension of said opening extending toward and being in line with a pouring spout on said drum and said throat opening Eellitg spaced from said spout for rapid draining of the 7. In an induction furnace comprising a housing having a refractory lining, said lining having a throat opening therein in communication with the interior of said housing, an elongated melting channel parallel to and below said throat opening, and an inductor unit interposed between said throat opening and melting channel, one end of said melting channel along its major dimension being positionable at a greater elevation than its other end.

8. In a rotary drum type induction furnace comprising a cylindrical drum having a refractory lining, said lining having an elongated throat opening therein, said throat opening being in communication with the interior of said drum, an elongated melting channel parallel to and be- References Cited by the Examiner low said th oat opening, and an inductor unit interposed UNITED STATES PATENTS between said throat opening and melting channel, the a major dimension of said opening and melting channel 2162502 12/37 Summey 1329 2,474,443 6/ 49 Tama et al. 13-29 extending in a direction substantially perpendicular to 5 a A the longitudinal axis of said drum, and means for ro- 3,092,604 6/63 Tam? tating one end of said melting channel along its major T dimension to a position where it is at a greater elevation RIChARD WOSD P 1mm y Examiner than its other end. ANTHONY BARTIS, Examiner. 

7. IN AN INDUCTION FURNACE COMPRISING A HOUSING HAVING A REFRACTORY LINING, SAID LINING HAVING A THROAT OPENING THEREIN IN COMMUNICATION WITH THE INTERIOR OF SAID HOUSING, AN ELONGATED MELTING CHANNEL PARALLEL TO AND BELOW SAID THROAT OPENING, AND AN INDUCTOR UNIT INTERPOSED BETWEEN SAID THROAT OPENING AND MELTING CHANNEL, ONE END OF SAID MELTING CHANNEL ALONG ITS MAJOR DIMENSION BEING POSITIONABLE AT A GREATER ELEVATION THAN ITS OTHER END. 